1. Field of the Invention
The present invention relates to pure crystalline racemic sodium parahydroxymandelate, the process for its preparation and its uses. It relates more particularly, by way of novel industrial product, to anhydrous crystalline racemic sodium parahydroxymandelate or racemic sodium parahydroxymandelate crystallized with one molecule of water free from any ions of chloride, acetate, formate, sulfate group and the like.
2. Description of the Prior Art
Certain salts of racemic parahydroxymandelic acid are described in the literature. Calcium parahydroxymandelate crystallized with 5.5 molecules of water and cinchonine parahydroxymandelate were isolated by A. ELLINGER et al., Z. Physiol. Chem., 65, 402-13, 1910. Intermediately, in the course of certain preparations of racemic parahydroxymandelic acid, either sodium parahydroxymandelate, or disodium 4-oxidomandelate have sometimes been obtained or used in aqueous sodium solution as, for example, in the alkaline hydrolysis of 4-dibenzoyloxy, .alpha. phenylacetamide according to J. ALOY et al., Bull. Soc. chim. France, 4, 11, 389-93 (1912) or of parahydroxyphenyltrichloromethylcarbinol according to H. HAAKH et al., Austrian Patent No. AT 141 159 or of ethyl parahydroxymandelate according to K. LANDENBURG et al., J. Amer. Chem. Soc. 58, 1292-94 (1936) or in the condensation of glyoxylic acid with phenol according to French Patent Application No. 78 31.123 of Nov. 3, 1978.
More recently solid monohydrate sodium parahydroxymandelate containing sodium chloride (about 10% by weight) has been isolated from its aqueous preparing solution from glyoxylic acid and phenol with salting by sodium chloride (see Belgium patent 867.287, Chemical Abstracts, 1979, 90, 870 67 g).
Moreover referring to U.S. Pat. No. 4,154,757, anhydrous sodium parahydroxymandelate having a purity of 99% only and containing 1% by weight of sodium chloride, is obtained from the monohydrate form by azeotropic removal of the water using toluene or xylene as azeotroping solvent.
However, insofar as is known, pure crystallized racemic sodium parahydroxymandelate (i.e not containing other anions such as chloride, acetate, formate, or sulfate) in anhydrous form or with one molecule of water has never been either isolated or described. Such a product free of chloride ions is suitable for preparing parahydroxybenzaldehyde by degradative oxidizing decarboxylation in a stainless steel reactor.